Radio receiver



RADIO RECElVER Filed oet. 27, 1932 4 Sheets-Sheet `1` Dec 21, 1937. E, P 'ANDREWS I2,103,135

, RADIO RECEIVER' vFiled-oct. 27, 1952 4 shams-.sheet 2 Jrz :fe n for:

y n eawfdfdnmw @Hr/zag Dec. 21, 1937. `E. F. ANDREWS 2,103,135

RADIO RECEIVER Filed oct. 27, 19:52 4 sheets-sheet :s

Dec. 21, 1937.

E. F. ANDREWS RADIO RECEIVER Filed Oct. 27, 1952 4 Sheets-Sheet 4 Ef/MZ@ v Patented Dec.`21, 1.937 i l Edward F. Andrews, Chicago, Ill. Application October 27, -1932, Serial No. 639,821

15 Claims.

This invention relates to radio receivers and has for its principal object toprovide a receiver.

energized by direct current and including an interrupter to render said current transformable and provided with means for preventing highl frequencysenergy from the interrupter from being impressed to an objectionable extent upon the `amplifying tubes.

A further object of the invention is to provide a receiver of this type in which the interrupter.

amplifying tubes and the means for isolating the undesired frequency are located in-compact relation within a single housing. l

Other objects, advantages and capabilities of the invention will vappear from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawings, in which- Figure 1 is a diagram of a radio receiver emi bodying my invention;

Fig. 2 is a diagram of the alternating current cable and switch plug for the receiver;

Fig. 3 is a diagram of the direct current cable and switch plug for this receiver;

Fig. 4 is a, diagram showing the energy supply part of a modified receiver;

- Fig. 5 is a diagram of a direct current lcable -and switch plug used in the embodiment of the invention illustrated in Fig. 4; i

Fig. 6 is a sectional view through the receiver; Fig. '7 is a plan view thereof with the cover removed; r y

Fig. 8 is an elevational view of the receiver, the casing being 'shown in section;

Fig. 9 is a diagram showing the energy supply Dart of a further modified receiver.

Fig; 10 isa diagram of a direct current cable and switch plug used in the embodiment of the invention illustrated in Fig. 9, and

Fig. ll is a diagram of an alternating current cable and switch plug for this receiver.

Referring to the drawings, the reference numeral I0 designates the antenna while the tubes of the setvare designated I2, I3 and I4. The speaker cone is designated I5 and the field coil and the voice coil by the reference numerals I6 and. I1, respectively. It will readily be understood from the following description that many novel and valuable-features of the invention may be'utilized'in sets having differenteircuits and that it is not intended to limit the invention to a setof the wiring system shown. lThe particular set herein selected for'the purpose of illustrating the invention isv a simple .four tube superheterodyne, the tube being the first detector prises two other windings 2| and 22.

(Cl. o-27) and oscillator, tube I2 the intermediate frequency amplifier, tube I3 the second detector, and tube |4 the audiofrequency power amplifying tube.

'I'he transformer I8 and rectifying tube I9 are provided for supplying. plate currentv of appropriate voltage fo'r the operation of the set. vThe plate of the rectifier I9 is connectedto winding 20 of transformer I8. This transformer com- A group 31, Fig. 1, of contacts 23, 24, 30, 3|, 34, 28 and 36 is mounted on the receiver and is adapted tocooperate witheither of the switch plugs 42 and 65 hereinafter described. One end of winding 22 of transformer I8 is connected to contact 23. The other end of winding 22 is connected to a magnetically operated interrupter 11 and to contact 29 of a double pole double throw vswitch 26.- Interrupter 'I1 comprises a magnet,

excited- 'by a coil 19, and contacts 80 one of which is stationary and the other carried by a vibrating armature. 'I'he connection from winding 22 to the interrupter 11 is completed through coil 1,9 and contacts 80 to pole 25 of switch 26.

' Condenser 82 is connected across coil 19 and contacts 80 to prevent arcing at the contacts and to minimize interference resulting from the opu eration of the interrupter. This interference is further reduced by means of a metallic casing 'I8 completely shielding the interrupter and connected to the .chassis of the set. This casing'is preferably lined with sound insulating material. A relatively high resistance 8| may be inserted across the points 80 to reduce the voltage built up across the points. One end of winding 2| of transformer I8 connects to contact 24. v The other end of winding 2| is connected to a, lsecond pole -32 of thev double pole double throw switch 26. Contact 33 of the switch is connected to contact and contact 35 is'connected to contact 3| and one end of winding 20 of the transformer.

The. other end of winding 20 connects to plate 46of a rectifier tube I9. Contact 34 connects t0 `one end of thev speaker field coil I6 through a radio frequency choke coil 54. The other end of 'field coil I6 connects to the common ground. of

` are connected together'and to pple 25' of switch 26 by means of conductor 86. For operation of the set on alternating curren a cable 38, Fig. 2, is provided'. This cable consists, of two conductors 40 and 4| connected at 55 one end to the prongs of a plug 39, adapted toplug into a conventional outlet box. 'I'he other end of cable-38 carries 4a switch plug 42 having a plurality of contacts, designated 41, 48, 49, 58, 5|, 52 and 53, corresponding to the contacts 24, 30, 3|, 34, 28, 2.3 and 36 of group .31 and adapted to be engaged with them respectively when the switch l plug 42 is applied to said group. Conductors 40 and 4| are connected to contacts 41 and 48, respectively, of switch plug 42. Contacts 49 and 50 are connected together by a'conductor -43 while contacts 52 and 53 are connected together by conductor 44. Contact 5| is left open.

With-switch plug 42 engaged with the contacts of group 31 and switch 26 thrown with its poles in the up position, as viewed in Fig. 1, the set is connected for alternating current operation. Winding 2| acts as the primary and connects to the prongs. of plug 39 through switch pole 32, switch contact 33, contacts 24 and 30 of group 31, contacts 41 and 48 of switch plug 42 and conductors 40 and 4I in cable 38.

Winding 22 supplies current to the filaments of tubes II, I2, I3, and I4 and rectifier tube I9, one end of the filaments being connected by means of conductor 86, switch pole 25, and switch contact 29 to one end of winding 22. The'other ends of the filaments are grounded to the chassis and the other end of the winding 22 is likewise grounded to the chassis through contact 23, contact 52, conductor 44, contact 53 and contact 36.

In this condition of switching, the winding 20 of transformer I8 acts as the secondary. One

sis ground. The other end of winding 28 is connected to plate 46 of rectifier tube I9.

Resistors 55 and 56 are connected across the speaker field coil I6 to utilize part of the voltage drop across the speaker field coil as grid bias voltage, which is applied to output tube I4.

Cathode 51 of rectifier tube I9 connects through radio frequency choke coil ,58 andthrough the various coupling devices to the plates of the tubes to supply the plate voltage. Resistor 59 reduces this Voltage to a suitable value to be applied to the screens of the various tubes while resistor 6| further reduces this voltage to the required value to obtain grid bias for tube I2. Variable resistor 68 is the volume control. l The rectified output of rectifier I9 is suitably filtered by condensers 62 and speaker field coil I6 which acts as a choke coil. The tuning of the set is accomplished by means of .variable condensers 88 and 89 which may be operated by a common shaft. Increased sensitivity may be obtained by introducing a small amount of regeneration in the second detector tube I3. 'I'his is accomplished by means of a small tickler coil 64 connected in the plate circuit of tube I3 and inductively coupled to the grid circuit of this tube.

In order tov adapt the set for use with direct current, as for example from an automobile storf age battery, the switch plug 42 is removed and replaced by a switch plug 65, Fig. 3.l This switch plug consists of a. plurality of contacts designated 81 connects at one end to contact 10 of switch plug 65 and, at the other end, to the positive' pole of the battery 83. Conductor 15 of the cable 81 connects at one end to contact 1I of switch plug 65 and, at the other end, to the negative pole of battery 83. Contact 12 of switch plug '65 connects to one end of the metallic shield 16 around the cable. The other end of this shield connects to the negative pole of the battery 83 and acts as a. third conductor of the cable.

When the. switch plug 65 is engaged with the contacts of group 31 and switch poles 25 and 32 are in the down position, -as viewed inKFig. l, the set is connected for direct current operation. In this case-winding 22 acts as the primary of transformer I8. One end of winding 22 is connected to the negative pole of the battery 83 through contact 23 of group 31, contact 1I of switch plug 65 and conductor 15 in cable 81. The other end of winding 22, or a suitable tap thereof, as' suggested at 45 in dotted lines on Fig. 1, is connected to the positive pole of the battery through coil 19 and contacts 80 of interrupter 11, pole 25 and switch contact 21 of switch 26, .contact 28 conductor 14 in cable 81.

When so connected the interrupter 11 will opv erateto interrupt the current through the circuit and supply a pulsating current to the winding 22 which produces an alternating current; of higher voltage in windings 20| and 2| of the transformer. plate 46 of rectifier tube I9. The other end of winding 2|I is connected to one end of winding 2| by means of pole 32 and switch contact 35 of switch 26. The other end of winding 2I connects to contact 24 of group 31, contacts G6 and 69 of switch plug 65 by means of conductor 13 and from Contact 34 of group 31 to speaker el-:l coil I6. In this manner windings 28 and 2| are connected in series Vto act as the secondary of transformer I8. The plate 46 of the rectifier tube is by-passed to contact 34 by a condenser 85. The condenser being in shunt with windings 20 and 2| prevents the voltage in these windings from attaining an excessive value during that part of the cycle when no current is passing through the rectifier.

be of the proper capacity for efciency and proper functioning of the interrupter contacts.

The filament current to the tubes is supplied by the battery through conductor 14 and shield 16 of cable 81. The positive pole of battery 83 is connected through conductor 14,-contact 18 of switch plug 65, contact 28 of group 31, switch contact 21 and pole 25 of 'switch 26, and conductor 86 tothe filaments of the tubes. The negative pole of battery 83 is connected through shield 16 of cable 81, contact 12 of switch plug 65, and contact 36 of group 31 which is connected to the chassis.

Itv will be seen that the circuit from the positive pole of battery 63 through conductor 14, contact 10, contact 28, switch contact 21, and switch pole 25 is common to both the filament circuit and the interrupted primary circuit whereas the negative side of the filament circuit is completed to battery 83 by means of metallic shield 16 of cable 81 and the .primary circuit is made through conductor 15 of cable 81. It has been found that when a common circuit is used from the battery tothe set, to furnish 'both' filament and primary current, an objectional interference is sometimes created due to the coupling of the filament,

One end of winding 20 is connected to This condenser should be lcapable of withstanding high voltages and should common battery conductors.

circuit tol-the interrupter circuit through the When the interference from this source is of suilicient intensity to be objectionable it may be overcome as shown V a plug adapted to engage in a socket on the chassis of the receiver. The shield case 18 of the vibrator is preferably lined with sound absorbing material to reduce the audible sound of the interrupterwhen in operation.

It will be seen that switch 26 serves as the on and off switch for the set.Y When the switch plug 42 is engaged with the set and the poles of switch 26 are in the up position, as viewed in Fig. 1, the set is'on, and when the poles of switch 26 are in the down position the set is off. When switch plug 65 is engaged with the group of contacts 31 the set is off when poles of switch 26 are in the up position, as viewed in Fig. 1, and on when the poles are in the down position. Switch 26, in conjunction` with conductor 13 in switch plug 65 and conductors 43 and 44 in switch plug 42, serves to complete the circuits for operation of the set on either alternating or direct current. The circuit arrangement, Fig. 1, is such that the set may be operated on alternating current with interrupter 11 Aremoved from the' set.

It will appearthat if desired this change over could be performed by plugs alone or switch alone` by a suitable multiplication of contacts. It is, however, preferred to provide the contacts of group` 31 in the form of prongs mounted on the edge of the base of ,the set, the switch plugs 42 and 65 being plugs provided with contacts in the form of sockets adapted to receive said prongs.

Fig. 4 illustrates the. transformer circuit of a modified embodiment of the invention. In this modification a double pole single throw switch 63 is used and the interrupter' is not incorporated in thel set.

The group |I2 of contacts, in the set, consists of seven contacts designated 88 to 94' inclusive.

One vend of winding 22 of transformer I8 is connected to Contact 93. The other end of winding 22 connects to' contact 92 through pole 95 and switch contact 96 of switch 63. A conductor 86 connects to switch. pole 95 to furnish filament current to the tubes, theI filament circuit being completed as shown in Fig. 1. One end of winding 2| connectsto contact 88. The other end of winding 2| is connected tocontact 89 through end of winding 20 connects to plate 46 of rectifier tube, I9. The other end of winding 20 is connected to contact 90. Contact 94 is grounded to the chassis.

cable aa,- Fig. 2, is used with this einternment of the invention for operation of the set on4 connection is made' by conductors 40 and 4| in cable 38, contacts 41 and 48 of switch plug 42 to contacts 88 and'89. Contact 88 connects to one rent for the tubes.

' switch contact 98 and pole 91 of switch 63. One

end of winding 2|. The other end of windingll is connected to contact 89 through switch contact 98 and pole 91 of switch 63.

Winding 22 serves to furnish the filament cur- One end of winding 22 is connected to the filaments of the tubes by means of conductor 8 6. 'Ihe other end of winding 22 connects to contact 93. The circuit is then completed throughcontact 52, conductor 44, and contact 53, in switch plug42, to contact 94 which is grounded tothe chassis of the set. acts as the secondary, one end` of this winding 20 being connected to plate 46 of rectifier tube I9, and the other end connecting to contact 90. From contact 90 the circuit is completed through contact 49, conductor 43 and contact 50 of switch plug 42 to -contact 9|. Contact 9| connects to l0 Winding 20 radio frequency choke coil 54 and then to speaker y field I6 as shown in Fig.- 1.

For operation of this modified set on direct current a cable 84, Fig. 5, is provided. This cable consists of two conductors 99 and |00 and a metallic shield I0| around the two conductors. An interrupter 11, similar to that shown in Fig. I, is connected in series with conductor |00 lin cable 84. A switch plug is carried by one end of the cable. The other end of the cable connects to a battery 83. The positive pole of battery 83 is connected to contact |06 of switch plug I|| by means of conductor 99. Contact |08 is connected to the negative pole of battery 83 by means of the metallic shield |0|, around the cable. Contact |01 of switch plug also connects to the negative pole of battery 83 'through conductor |00, and coil 19 and contacts 80 of interrupter 1,1. connected by a conductor |09 while contacts |03 and |04 are connected by a conductor ||0.

With switch plug I in engagement with contacts of group ||2 and switch 63 with its poles in the lower position, as viewed in Fig.v 4, the circuit is complete fordirect current operation. In this case the winding 22 serves as the primary of transformer I8. One end of winding 22 connects to contact 93 of group' I I2 through contact |01 of switch-plug conductor |00 in cable 84, coil 19 and contacts 80 of interrupter 11 to the negative pole of battery 83. The other end l of winding 22 connects through pole 95 and contact 96 of switch 63, contact 92, contact |06 of switch plug and conductor 98 of cable 84 to the positive pole of battery-,83. This circuit also supplies current to the filaments of the tube in the set by means of conductor 86. The circuit to the grounded ends of the filaments is made from the chassis through contact 94, contact |08 of switch plug f and through the metallic shield |0| of cable 84 to the negative pole of the battery 83. The interrupter 11 is completely enclosed in a shield case 18 and aresistance 8| anda condenser 82 is provided as previously described in connection with Fig. 1. 18 is connected to shield |0| of cable 84.

` Windings 20 and 2| areconnected in series to form the secondary .of transformer I8. One end of winding 20 connects to plate 46 of rectifier tube |9. The other end of winding 20 connects to one end of winding 2| through contaot 90, contact |04, conductor ||0 and contact |03 of switch plug contact 89, contact 98 and pole 91 of switch 463. The other end of winding 2| connects by means of contact 88, contact |02, con- `4ductor |09 and contact |05 ofswitch plug and contact 9| to speaker field coil I6 as in Fig. 1.

Contacts |02 and |05 of switch plug |I| are Shield case invention, when poles of switch 83- are in the lower position, as viewed in Fig. 4, the set is on for either alternating current or direct current operation and with the poles of switch -83 in the upper position the set is off in both cases. This permits the switch to be mounted on and operated b y the volume control 63.

When th'e set is being operated on direct current, winding 22 of transformer I8 is the primary while windings 23 and 2| are connected in series to form the secondary. When the set is operated on alternating current, winding 2| acts as the primary, winding 23 as the'secondary and form of an inverted dish. The underside of this base accommodates the wiring and various small parts such as resistors and by-pass condensers. A loud speaker 4, preferably of the cone type, is mounted in the center of the base with the apex of the cone pointed towards the base. Suitable spacers may be employed between the field pot |I5 and the base ||3 of the set, if necessary to bring the rim |I8 of the speaker cone to a suitable height to accommodate the tubes and 38 other apparatus mounted on the base therebeneath.

The component parts of the radio set such as the tubes II, I2, I3, I4 and I3, transformer I8, condensers 88 and 83, lter condensers 32,-and

optionally the interrupter. 11 are mounted on the base in the 'space available around the speaker eid pot. The tubes and their associated coupling transformers are-mounted at the periphery of the base with their axesperpendicular to `the base.

A decorative cover- I |1, adapted to be supported by rim IIS of speaker II4, is placed over the set. The cover may be fastened to rim AI I5 by a number of screws I|8 having decorative heads. The

top surface of cover |I1 directly over the speaker cone is perforated to permit egress of sound from the speaker cone. Thecover ||1 entendsk downwardly to a point somewhat above the lower edge 'of base II3. The diameter of the cover at 58 this point is somewhat greater than the diameter of the base I I34 so as to provide an annular opening |I3 to permit egress of sound waves from theunderside of speaker. In this manner the cover I |1 forms an effective baille for the speaker.

Shaft |22 for operating condensers 88 and 83 and volumecontrol shaft I2| project above the top'of the cover II1. Knobs |23 are carried by shafts |2.| and |22 and are adapted to be easily removed.' Thus it will be seen that to obtain.

'scale |23is formed as at |25 and an opening |24- provided for convenient observation of the scale by the operator.

The contacts ofthe group 31 are mounted onY base I I3 in definite order and the contacts of the 4contacts of the group 31 may suitably be in the form of prongs while the contacts of the switch plugs may suitably be sockets providedA in said I plugs.

In the modification of the invention shown in Figs. 9, 10, and 11, the tubes II, I2, I3, I4 and I3 are similar to those of the same numbers in the l previously described modifications. The transl0 former I8 is substantially similar and comprises the windings 23, 2| and 22. The interrupter 11 is'substantially similar and its stationary contact 83 is grounded. 'I'he other end of the winding 13, that is the end remote from the'vibrating conll tact 83 is connected to one end of the winding 22. The other end of the winding 22 is connected to a contact |21 and to a. conductor |28 which serves to supply current to the filaments of all the tubes II, I2, I3, |4 and I3. The other ends 20 of the filaments are grounded. The contact |21 is adapted to be connected to a contact |23 by means of a switch pole |33, when in its uppermost position, as viewed in Fig. 9.

In this modification the receiver is provided 25 with a group |3| of contacts which are analogous to group 31 and group ||2 ofthe previously described modifications. The group |3I comprises contacts |32, |33, |34, |35, |33, |31 and |38. Contact |23 is connected to contact |32. Con- 3 tact |33 is connected to a contact |33 which is adapted to be connected to a contact |43 by the pole |33 when in its lower position, as viewed in Fig. 9. The contact |43 is shown connected to a suitable tap of winding 2|, althoughl it may be 33 connected to the upper end thereof if desired, other steps being taken to attain the necessary correlation between the windings 23, 2| and 22. Contact |34 is connected to the upper end of the winding 2|. The other end of the winding 2| 40 is connected to contact |33. Contact |35 is connected to one end of the winding 2|).` The other end of the winding 28 is connected to the plate of the' tube I3. Contact |31 is connected to the field coil I6 of the speaker I5 in substantially the same u manner as describedheretofore., Contact |38 is grounded.

In order to adapt the set for use with direct current supplied by a battery |4I, a switch plug |42 isemployed having contacts |43, |44, |45, |46, I 41, l. |48 and |43 corresponding to contacts |32, |33,

-nected to the group |3| of\c\ontacts, the negative plate of the battery |4| is grounded through the shield |5| and contacts |43 and |38. Contact |44 being left open, contacts |33 and |33 are disconnected and the off position of switch |33 is its 65 lower position, as viewed in Fig. 9. The positive plate of the battery |4I isv connectedthrougn contacts |43, |32 and |23, the switch pole |33 (in its upper position), and contact |21 to the winding 22 and the conductor |28. 7.

The` current passing through the winding 13 actuates the interrupter 11 as described before, and winding 22 serves'as the primary for the transformer I8. windings 23 and 2| are connected in sexies through contact |35, contact |48, 7|'- |34 and |38. Contacts |54'and |51 are connected to the prongs of the plug |60 which. may be inserted in any suitable power outlet supplying alternating current. Contacts |56 and |58 are connected. When the switch plug |52 is applied to the group |3|, contacts |54 and |51 communicate to contacts |33 and |36- so that the winding 2|, or the lower portion thereof, is energized when.l

the switch pole |30 is moved to its lower position as viewed in Fig. 9, this being the on position for the alternating current hook-up. When the switch pole |30 is moved to its upper position, the set is oii. Contact |53 is isolated and winding 22 serves as a secondary, supplying filamentv current to the conductor |28. This current passes through the filaments to ground and also passes through winding 19 and contact 80 to ground. This current is, however, relatively slight and does not affect thevibrator 11. Winding 20 is connected through contacts |35, |56, |58, |31, and thus tothe field coilin the manner previously referred to.

An important result obtained by this modification is that the production of radio frequency disturbances by the vibratorA 11 is reduced to a minimum, particularly owing to the manner in which the interrupter is directly grounded. In order further to reduce interferences it is preferred to provide Choke coils |6| and |62 in the line |28. It will be noted that c'oil |62 is provided between tubes |2 and I3 Vand that coil |6| is located on theoutput side of tube I4. The inductances of the choke coils |6|,'- |62 are correlated to the resistances of the filaments to prevent voltage disturbancesfrom passing along the conductor |28 in the output-to-input direction. The-choke coils ISI, |62 combine with the filaments to provide a, filter circuit containing inductances and resistances. Filtering action is greatest at the filaments of the tubes I and I2, which is important since disturbances in these tubes are capable of greater amplification in the final output.

Other important effects obtained by this modiiication are its great simplicity, considering the results attained, and the fact that the switch employed may be of simple and heavy construction while taking up a very small amount of space. v A

Although the invention has been disclosed in connection with the specific details of preferred embodiments thereof, it must be understood' that such details are not intended to be limitative of the invention except in so far asset forth in the accompanying claims.

Having thus described my invention, what I claim as new and desire' to secure by Letters Patent of the United States is:

1. In 'a radio receiver, in combination, thermionictubes having filaments and plates, a transformer adapted to be energized from a source of alternating current or from a source of 'directcurrent, a conductor conveying current to said laments, said filaments being arranged in parallel, an interrupter adapted continuously to interrupt the direct current supplied to the transformer, and choke coils in series in said conductor between said laments through which coils said filaments are connected to said source of direct current when the set is operated by direct current, for the purpose of preventing the amplication through said tubes of electrical disturbances created by said circuit interrupting means. y 2. In a radio receiver, in combination, thermionic tubes having filaments and plates, a transformer adapted to beenergized from a source of direct current, an interrupter adapted continuously to interrupt the direct current supplied to the transformer, a conductor supplying current to said filaments which are arranged in parallel, and a plurality of choke coils in series in said con:

ductor at least one of said choke coils beingy between said laments for the purpose of pre.

venting the amplification through said tubes of electrical disturbances created by said circuit interrupting mea-ns. v I

3. In Ia` radio receiver, in combination, thermionic tubes having iilaments and plates, a. transformer adapted to be energized from a low voltage storage battery, an interrupter adapted continuously tointerrupt the direct current -supplied to the transformer, said transformer having. a secondary adapted to supply high voltage current for said plates, a conductor supplying current to said filaments which are arranged in parallel, and

aplurality of choke coils in series in said conductor at least one of said coils being between said laments from said interrupter and preventing the amplicationv of electrical disturbances from the interrupter in said tubes, said tubes, interrupter and transformer being mounted close together in a compact unit.

4. Ina radio receiver, a series of tubes con-- nected in cascade progressively to amplify a sig'- nal from input to output of said series, said tubes having filaments with one end grounded, a source of filament current containing an undesiredlhigh frequency component, having one side grounded,

a conductor connecting the ungrounded ends of' the' filaments together, a high frequency choke coil in saidcondurctor betweenthe input land output end of y said series, a second conductor connected to the first conductor at the output end of said series oi tubes and with the ungrounded sideof said source of filament current,

and a chokel coil in the second conductor, said choke coils having impedances so proportioned to the resistances of the d filaments to constitute therewith an effective filter progressively attenuating the undesired component towards the input end of said series.

5. Ina radio receiver, a series of tubes connected in cascade progressively to amplify a signal from input to output of said series, said tubes' having filaments with one end grounded, a source of lament current, a continuous interrupter giving an undesired high frequency component to said lament current, said source and interrupterv having one side grounded, a conductor connecting the ungrounded ends of the filaments to.- gether and connecting the filaments to the ungrounded side of the source of filament current, and a choke coil in said conductor having an impedance proportioned tothe resistances of the filaments to constitute therewith an effective iilter attenuat'ing the undesired high frequency, said tubes and interrupter being located in compact relation within the receiver. d

6. In combination, a battery having one lside grounded, and a battery operated radio receiver comprising a series of tubes connectedin cascade progressively to amplify a signal from input to output of said series, said tubes having filaments eor with one end grounded, a continuous circuit interrupter having one side grounded, the other being connected to the ungrounded side of the battery, a conductor connected to the ungrounded ends of the filaments and connecting the lament at the output end of the series to the ungrounded side of the battery, and choke coils in said conductor correlated with the resistances of thelaments to constitute an eiective filter for objectionable high frequency energy produced by said interrupter, attenuating said high frequency energy progressively from the output to the input end of the series, said tubes and interrupter being located in compact relation within said receiver.

7. A battery operated radio receiver comprising a base, a loud speaker, thermionic tubes, other radio apparatus and a current interrupter, a

housing cooperating with said base to enclose the paratus and a current interrupter all located in compact relation Within said housing, said thermionic tubes having f'llaments energized from the battery which supplies current to the interrupter, and a choke coil in the circuit'between said interrupter and said filaments.

9. In a battery operated radio receiver, in combination, a plurality of thermionic tubes havl ing plates and filaments, a step-up transformer having a primary Winding and a secondary winding, a rectifier connected to the second winding for supplying high voltage to said plates, vibrating means supplying pulsating low voltage direct current to the primary winding, a low resistance, high frequency choke coil, and other receiving apparatus, a metal support carrying the aforesaid devices and a common housing enclosing them, a low voltage battery external to said -housing for supplying current to said filaments and to said vibrating means, one terminal of said battery being connected to one side of said filaments and one side of said vibrating means and primary winding circuit, and conductor means connecting the other terminal of said battery to the other side of said filaments and the other side of said vibrating means and primary winding circuit, said choke coil being connected in series with said conductor means between said filaments and said vibrating means and primary winding circuit for attenuating the high frequency current produced by said vibrating means in the filament circuit. i

10. In a battery operated radio receiver, in combination, a plurality of thermionic tubes having plates and filaments, a step-up transformer having a primary winding and a secondary'winding, a rectifier connected to the secondary winding for supplying high voltage to said plates, vibrating means supplying pulsating lowA` voltage direct current to the primary winding, a plurality of low resistance, high frequency. choke coils, and other receiving apparat-usa metal support carrying the aforesaid devices and a\ one side of said vibrating means and primary winding circuit, the other terminal of said battery being connected to the other side of said :filaments and the other side of said vibrating means and primary circuit, said choke coils being connected between the input tube of said receiver and said vibrating means and primary circuit for attenuating the high frequency current produced by said vibrating means in the filament circuit.

,11. In a radio receiver, in combination, a battery, a metal base to which one side of said battery is grounded, a plurality of thermionic tubes mounted on said base and having plates and filaments, said filaments being grounded to said base, a continuous current circuit interrupter mounted on said base and having one side connected to said grounded side of the battery, a transformer mounted on said base and having a winding in the interrupter circuit, a rectifier deriving energy from said transformer and delivering high voltage direct current to said plates, conductor means between the ungrounded side of the battery and the ungrounded side of the interrupter circuit and the ungrounded side of the filaments, and a choke coil in said ungrounded conductor means between the interrupter and the filaments.

12. In a radio receiver, in combination, a battery, a plurality of thermionic'tubes having plates and filaments, a continuous circuit interrupter, a transformer having a winding in the interrupter circuit, a rectier deriving energy from said transformer and delivering high voltage direct current to said plates, a common ground to which one terminal of the battery, one side of each filament and one side of the interrupter circuit are grounded, conductor means between the ungrounded side of the battery, thev ungrounded side of the interrupter-circuit and the ungrounded side of the filaments, and a choke coil in said conductor means between the interrupter and the filaments.

13. In a radio receiver; in combination, a battery, a metal base, apluraiy of thermionic tubes having plates and filaments mountedy on said y base. a continuous circuit interrupter mounted grounded to said metal base, conductor means between the ungrounded side of the battery, the ungrounded side of the interrupter circuit, andl the ungrounded sides of the filaments, said choke coil being connected in said ungrounded conductor means filaments.

14. In a radio receiver, a series of tubes connected in cascade vprogressively to amplify a signal from input to output of said series, said tubes having filaments, a source of filament current, a continuous circuit interrupter givin/gI an undesired high frequency component to said filament current, conductor means connecting one end ofeach lament together and connecting the filaments to the source of filament current, and a choke coil in said conductor means having between the interrupter and the an impedance proportioned to the resistances of v 2,108,135 the illaments to constitute therewith an eii'ective l lter attenuating the undesired high frequency, said tubes and interrupter being vlocated in compact relation within the receiver. 15. In combination, albattery and a-.batte operated radio receiver comprising a series of tubes connected in cascade progressively to amplify a signal -from input to output of said series, said tubes having ilaments, a continuous circuit interrupter connected to the battery, conductor means connected to one end of each iilament and connecting the laments 'to the battery, and atleast two choke coils in said conductor means correlated with the resistances ofthe iilaments to constitute an effective filter `for objectionable high frequency energy produced by said interrupter, attenuating said high frevquency energy progressively from the output to the input end oi the series, said tubes and interrupterbeing located in compact relation within said receiver. v

EDWARD F. ANDREWS.A 

